This invention relates to a coating resin composition. Particularly, this invention relates to a coating resin composition which can give a film excellent in properties such as adhesion, gloss or the like without a primer treatment to polyolefins which has not been subjected to any surface treatment for affording printability such as primer treatment, said polyolefins having been formed into molded articles, sheets, films, etc.
Recently, there have been attempted to use synthetic resins such as polyolefins or the like in place of metal for the purpose of weight saving, rust prevention and the like in the field of various industrial fields of automobiles, domestic electric appliances, etc. In this case, coating is generally applied on the surface of a molded article, because the surface of the molded article is required to be in good condition. However, coatings applied on the surface of molded articles made from plastics such as polyolefins, for example polyethylene, polypropylene or the like are generally poor in film performances such as adhesion, gloss, surface appearance or the like. Therefore, there have hitherto been proposed many attempts in order to improve the film performances such as adhesion of the coating to a molded article made from plastics such as polyolefins or the like, gloss, surface appearance or the like. For instance, one of the methods for improving adhesion is to subject the surface of the molded article to surface treatment such as degreasing treatment, chromic acid treatment, etc. There is also a method in which the surface of the molded article is subjected to primer treatment by coating a chlorinated polyolefin or a polyolefin modified with maleic acid or anhydride thereof in a solution or a dispersion and a paint excellent in film performance is applied thereto (refer to, e.g. Japanese Patent Application Kokai (Laid-Open) Nos. 83042/83, 118809/83, 30830/84, etc.).
Furthermore, there have been proposed as paint compositions for improving the adhesion of films applied to polyolefin molded articles, epoxy compositions comprising a polyolefin or an ethylene copolymer which has functional groups reactive with an epoxy group, a hardner for an epoxy resin, and an epoxy resin (e.g. Japanese Patent Application Kokai (Laid-Open) Nos. 72053/81, 50971/81, 101122/83, etc.). There have also been proposed a urethane composition comprising an acrylic resin which has functional groups reactive with an isocyanate group, a chlorinated polyolefin and an isocyanate compound, and a urethane composition comprising an acrylic resin modified with a chlorinated polyolefin which resin has functional groups reactive with an isocyanate group and an isocyanate compound (e.g. Japanese Patent Publication No. 14767/82, Japanese Patent Application Kokai (Laid-Open) Nos. 17174/83, 27968/84, etc.). Moreover, there have been proposed chlorinated polyolefin resin compositions modified with an acrylate which comprise an acrylic resin and a chlorinated polyolefin (e.g. Japanese Patent Application Kokai Nos. 183718/83, 194959/83, 30830/84, etc.).
However, the methods of surface treatment mentioned above are often insufficient to improve film performances such as adhesion or the like. In the aforementioned method by primer treatment, a film excellent in adhesion is often obtained depending on the kinds of chlorinated polyolefins and modified polyolefins, although the method has defects that the handling operation for coating the primer is compricated and needs much time and effort for the primer treatment, thus leading to an increase of cost for coating. Moreover, it is difficult to say that the aforementioned epoxy compositions and urethane compositions are sufficient in adhesion to plastic molded articles made from, e.g. polyolefins or the like. These compositions are of a double-liquid type and thus need time for blending. They are of a curing type and thus have defects in that they should be considered for their workability such as pot life or the like.
The adhesion of the aforementioned chlorinated polyolefin composition modified with acrylates is influenced by the content of the chlorinated polyolefin. Thus, the composition tends to decrease their performances such as the surface appearance, gloss or the like, even if sufficient adhesion is afforded to the composition by increasing the content of the chlorinated polyolefin. Thus, the composition also has a defect in that it is difficult to modify simultaneously adhesion, surface appearance and gloss.